【作者】 朱孟正；

【导师】 樊锡君；

【作者基本信息】 山东师范大学 ， 光学， 2004， 硕士

【摘要】 无粒子数反转激光(Lasing Without Inversion简称LWI)的研究是当前国际上激光物理重要而活跃的研究前沿领域之一，无粒子数反转激光的研究不仅具有重要的理论价值，而且有广阔的应用前景。作为一种产生激光的新型机制，应用无反转激光可以在应用传统激光理论和方法很难甚至不可能产生激光的高频光谱区，如X-射线甚至γ-射线区产生激光，因此近年来引起人们的很大兴趣。 本文首次提出了开放的四能级无粒子数反转激光系统模型，给出了其定态非线性解析解并讨论了系统各参数对产生无粒子数反转激光的增益、色散和粒子数差的影响；然后分别研究了驱动场位相涨落和传播效应对无粒子反转激光系统的影响。本论文共分四章： 第一章为综述，阐明了无粒子数反转激光的研究意义及产生的基本原理，并简单介绍了当前这一重要课题的研究现状和研究内容； 第二章在封闭的四能级无粒子数反转激光模型的基础上提出了开放的四能级无粒子数反转激光系统模型，并经过复杂的计算得到了其定态非线性解析解，利用解析解的数值计算结果分析了系统各参量变化对激光增益、色散及粒子数差的影响，讨论了线性和非线性的差别。 第三章讨论了驱动场位相涨落对开放的四能级无粒子数反转激光系统的影响。驱动场的相位涨落将导致一个有限的线宽，我们给出了驱动场存在相位涨落时系统的稳态解析解，然后利用此解析解分别讨论了有限线宽、探测场失谐、驱动场失谐和驱动场Rabi频率、探测场非相干泵频速率、原子退出速率和注入速率比对无反转激光增益和色散的影响。 第四章在不考虑Doppler效应和考虑Doppler效应两种情况下，对开放的四能级无中文摘要反转激光系统受传播效应的影响的研究。不考虑DopPler效应时，讨论了探测激光增益ImPI。·驱动场Rabi频率。和探测场Rabi频率g分别随传播距离的变化关系，并讨论了特定传播距离处探测激光增益随激光介质入口处驱动场Rabi频率的变化关系;考虑D即pler效应情况下，在驱动场、探测场和原子运动均同向传输时讨论了探测激光增益Imp，。·驱动场Rabi频率。和探测场Rabi频率g以及能级粒子数分别随传播距离的变化关系，特定传播距离处探测激光增益分别随分别激光介质入口处驱动场Rabi频率和DopPler展宽的变化关系;并对探测场、驱动场以及原子运动四种不同传输情况下的数值计算结果作了比较。更多还原

【Abstract】 The study of lasing without inversion (LWI) is an important and active research front field in international lasing physics nowadays. The study of LWI has not only an important theoretical value, but also wide application prospects. As a new mechanism of producing laser, LWI have received considerable attention for their potential to obtain laser light in spectral domains, e.g. the x-ray or even y-ray range, where conventional methods based on population inversion are not available or are difficult to implement.We presented at first the theoretical model of the open four-level LWI system. In this paper, we mainly studied the effect of system’s parameters varying on the gain, dispersion and population difference, and the effect of the driving field phase fluctuation and the effect of propagation on the open LWI system. This paper consists of four chapters.In Chapter 1, we explained the significance for studying LWI and the basic principle of producing LWI, introduced simply the current research state and the main contents for the important study subject at present.In Chapter 2, the model of an open four-level and its nonlinear analytical solution in the steady state were presented on the basis of the closed four-level system. Using numerical results from the nonlinear analytical solution, we analyzed the effect of system’s parameters varying on the gain, dispersion and population difference, and discussed the difference between the nonlinear and linear solution.In Chapter 3, we studied the effect of the driving field phase-fluctuation the open four-level non-inversion lasing system. The phase-fluctuation of driving field results in thefinite line-width of the driving field. We obtained the analytical solution in the steady state in the phase fluctuation of driving field. Using the numerical calculation results of the analytical solution, we discussed the effects of the finite line-width of driving field, the detuning of the driving and probe fields, the Rabi frequency of the driving field, the ratio of the atomic injection rates and the atomic exit rate on the gain and dispersion of the lasing without population inversion.In Chapter 4, under regarding the Doppler effects due to atomic motion and regardless of the Doppler effects, we studied the propagation effects on lasing without inversion in the open four-level system, respectively. When ignoring the Doppler effects, we discussed the effects of the propagation length on the probe gain, the Rabi frequency of the driving and probe fields, and discussed the effect of the driving field Rabi frequency at the entrance of the active medium on the probe gain for a propagation length of 5.2 cm. When considering the Doppler effects and the probe and driving fields and the atomic motion co-propagating, we analyzed the probe gain, the Rabi frequency of the driving and probe fields and the populations as the functions of the propagation length and studied respectively the probe gain for a propagation length of 5.2 cm as the function of the driving field Rabi frequency at the entrance of the active medium and as the function of the Doppler broadening. We contrasted the numerical simulation results in the four transmission cases among the probe field, the driving field and the atomic motion.更多还原